metamorphic
Weathered quartz-rich metamorphic rock, possibly quartzite
Quartzite; predominantly quartz (SiO₂), with minor feldspar, mica, and iron-oxide staining
AI-generated identification · may be incorrectHardness about 7 Mohs; tan, cream, and gray coloring with rusty brown weathering; vitreous to dull luster and a massive, granular texture. Quartzite lacks prominent cleavage and typically fractures irregularly or conchoidally.
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Physical properties
Hardness about 7 Mohs; tan, cream, and gray coloring with rusty brown weathering; vitreous to dull luster and a massive, granular texture. Quartzite lacks prominent cleavage and typically fractures irregularly or conchoidally.
Formation & geological history
Formed when quartz-rich sandstone was deeply buried and recrystallized under heat and pressure, commonly during regional mountain-building. Its exact geological age cannot be determined from the photograph.
Uses & applications
Used as crushed stone, road aggregate, building stone, countertops, and decorative material; attractive specimens may be collected but are generally low value.
Geological facts
Quartzite is harder and more tightly fused than its sandstone precursor; individual sand grains may be difficult to distinguish. The irregular surface and iron staining suggest substantial weathering.
Field identification & locations
Identify it by its very hard, quartz-rich texture and inability to scratch easily with a steel knife; dilute acid should not fizz unless carbonate minerals are present. Common in metamorphic mountain belts worldwide, including the Appalachians, Rocky Mountains, and Precambrian shields.
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